Process of making propellant powders



Patented July 24, 1934 UNITED STATES PROCESS OF MAKING PBOPELLANTPOWDEBS Gordon 0. Tibbitts and Frederick R. Seavey,

Alton, Ill., assignors to Western Cartridge Company, East Alton, 111., acorporation o! Delaware No Drawing. Application November 1,1930, SerialNo. 494,183. Renewed June 24, 1933 20 Claims.

This invention relates to propellant powders, and more particularlypowders of the type which are surface-treated with a deterrent to retardthe initial combustion rates. One of the objects of this invention is toprovide a process of surface treating propellant powders, and moreparticularly double base propellant powders, adapted to improve theballistic characteristics of such powders.

Another object is to provide a process of the character described,whereby the application of the deterrent to the powder grain can becontrolled to secure the desired penetration.

Further objects will appear from the detail 5- description, in whichwill be described an illustrative embodiment of this invention; it is tobe understood, however, that this invention is susceptible of .variousother embodiments.

In the surface treatment of propellant powders with a deterrent, it hasbeen found advantageous to apply the deterrent to be employed with avehicle which is a solvent for the deterrent. Such a vehicle may or maynot be a solvent for the powder grains. In applying a given surfacecoating to powder grains in this manner, i. e., by merely adding thesolvent solution of the deterrent to the powder, difliculty isexperienced in controlling the depth of penetration upon which variablethe ballistic properties of the finished powder are dependent. Also thegrains are liable to stick together due to the softening of theirsurfaces by the solvent or because of the adhesive properties of thecoating of the deterrent. Even where a highly volatile solvent is used,it is difllcut to evaporate this solvent quickly enough to preventsticking, and to secure the desired degree of penetration.

' Generally stated in accordance with this invention, the deterrent iscarried in a vehicle and applied to the powder grains by efiectlngdeposit of the deterrent on the grains. There are several procedureswhich have been found suitable to effect the deposit of the deterrentupon the grains. In accordance with an embodiment of this invention thedeterrent-is dissolved in the vehicle. The vehicle may or may not be asolvent for the powder grains. In order to effect deposition of thedeterrent, there is added an agent, preferably a non-solvent for boththe deterrent and the powder grains which is adapted to effectprecipitation of the deterrent from the vehicle. Where the vehicle isvolatile, it is separated from the surface-treated powder grains byevaporation. For this purpose, however, the heating of the mass iscarried out at a temperature and for a period of time sufilcient notonly to effect evaporation of the vehicle, but also to secure thedesired degree of penetration of the deterrent thus controlling theballistic properties of the finished powder. In the application of thedeterrent, carried by the vehicle, to the powder grains, the vehicle isapplied in an amount only suflicint to wet the grains and theprecipitation of the deterrent and the evaporation of the vehicle isthen proceeded with at the desired rate. In general, the process is socarried out that the contact of the deterrent-carrying vehicle, theprecipitation of the deterrent and the evaporation of the vehicle areall controlled so as to efl'ect the desired degree of penetration of thedeterrent into the grain thus imparting the desired ballistic propertiesto the finished powder.

In accordance with another embodiment of this invention, the deterrentcarried in solution in a vehicle, is dropped slowly onto the powdergrains which are in contact with an excess of a non-solvent for both thedeterrent and the powder. In this manner, the deterrent is precipitatedfrom its solvent solution immediately upon coming in contact with thenon-solvent and the deterrent being in very finely divided form isreadily picked up by the powder grains. For a given coating, the rate ofaddition of the deterrent solution and the temperature and time oftreatment maybe so controlled as'to effect the desired degree ofpenetration of the deterrent.

In order to generally accomplish the objects of this invention, thedeterrentmay be one of the usual ones employed for that purpose. Adeterrent which has been found particularly useful is diamyl phthalate;a related deterrent, dibutyl phthalate has also been found satisfactory.Moreover, deterrents, such as tricresyl phosphate, ethyl 95 lactate, andmono, di and trinitro toluene may be employed. 'Any coating material maybe applied by means of the principles outlined herein. The materialsused for this purpose may or' may not be plasticizers for thenitrocellulose of the powder grains. When the deterrent employed is nota plasticizer for nitrocellulose, the temperature and time of treatmentis so regulated that the desired degree of spreading rather thanpenetration is obtained.

It will be understood, of course, that suitable solvents may be employedwhich are adapted for the particular deterrents chosen and theparticular powder under treatment. The word modifier' is employed in theappended claims no inits usual sense in this art as contemplating thevarious substances employed for modifying or varying the burning rate orballistic properties of the powder, of which substances the so-calleddeterrents constitute a sub-class.

Many of the advantageous features of this invention may be secured bythe surface treatment of smokeless powder grains generally, whenemploying the principles embodying this invention. This invention isapplicable, therefore, to both powders of the straight nitrocelluloseand double base, or nitrocellulose-nitroglycerin types. This inventionhas been found particularly applicable to the treatment of double-basepowders, for example, a surface treated nitrocellulose-nitroglycerinwhich is of particular utility is one containing 15% nitroglycerin and6% diamyl phthalate.

As an illustrative embodiment of this invention, anitrocellulose-nitroglycerin powder grain containing 15% nitroglycerinis surface treated with diamyl phthalate in the following manner: Thedeterrent is carried in the vehicle such as methyl or ethyl alcohol,which is a mild solvent for the powder grain; however only sufficient ofthe vehicle is employed to wet the surface of the mass of powder grainsbeing treated. After the solution of the deterrent has been thoroughlyagitated with the powder being treated to the extent desired to securethe desired ballistic properties, the whole mass is drowned in water;the alcohol and water being completely miscible, the precipitation ofthe deterrent is accomplished. The water slurry of the surface treatedpowder, the alcohol and the water are then heated toa temperature of'75? C. and held there for thirty minutes to accomplish the evaporationof the alcohol from the solution. The grains can then be drained anddried in any suitable manner, and the grains, if desired, can begraphited. It is found that by varying the period of heating, differentballistic results are secured; accordingly, the time of treatment musthave reference to the desired ballistic properties.

There is thus produced a powder grain, in this particular instance, adouble base powder grain, having the desired ballistic properties. Thepowder is thus rendered progressive burning to the desired extent by thecontrol of time and temperature which factors govern the degree of pene.tration when employing a given amount of a particular deterrent. Thereis also secured an efficient and uniform distribution of the deterrentover the grains and on account of the presence of the non-solvent suchas water, sticking together of the grains is obviated. It will beunderstood, of course, that suitable means is provided to recover thesolvent in a manner well known to those skilled in the art.

As a further illustrative embodiment of this invention a powder grain ofstraight nitrocellulose composition is surface treated withdinitrotoluene in the following manner: The deterrent is carried insolution in the vehicle such as benzol or alcohol and this solutionisdropped into an agitated mixture of the grains with an excess of water.When the solvent solution comes in contact with the water, the DNT isprecipitated in a very finely divided condition and is applied to thegrains in a uniform layer. The degree of penetration of the deterrent iscontrolled to the desired extent by the time of treatment and thetemperature to which the mass is heated. The solvent is evaporated andrecovered. The grains may be drained and dried in any suitable mannerand then may be graphited, if desired.

It will be understood, of course, that either straight nitrocellulose ornitrocellulose-nitroglycerin grains may be surface coated by either oneof the illustrative procedures cited above. It will further beunderstood that various features and subcombinations are of utility andmay be employed without reference to other features and subcombinations;that is, contemplated by and is within the scope of the appended claims.It will be further understood that various changes may be made in detailwithout departing from the spirit of this invention; it is thereforeunderstood that this invention is not to be limited to the specificdetails described.

Having thus described the invention what is claimed is:

1. In the art of making propellant powders, the process comprising,treating powder grains with a deterrent dissolved in a vehicle andprecipitating the deterrent from the vehicle in the presence of thevehicle.

2. In the art of making propellant powders, the process comprising,treating powder grains with a deterrent carried in a vehicle and addingan agent adapted to effect deposit of the deterrent on the grains.

3. In the art of making propellant powders, the process comprising,treating powder grains with a deterrent dissolved in a vehicle andadding an agent adapted to effect precipitation of the deterrent fromthe vehicle.

4. In the art of making propellant powders, the process comprising,treating powder grains with a deterrent dissolved in a vehicle andadding an agent which is a non-solvent for the deterrent.

5. In the art of making propellant powders, the process comprising,treating powder grains with a deterrent carried in a vehicle which is asolvent for the powder grains and for the deterrent and adding an agentwhich is a non-solvent for the powder grains and the deterrent.

6. In the art of making propellant powders, the process comprising,treating powder grains with a deterrent carried in a.volatile vehicle,effecting deposit of the deterrent and thereafter evaporating thevehicle. I

7. In the art of making propellant powders, the process comprising,treating powder grains with a deterrent dissolved in a volatile vehicle,precipitating the deterrent from the vehicle and thereafter evaporatingthe vehicle.

8. In the art of making propellant powders, the process comprising,treating powder grains with a deterrent carried in a volatile vehicle,adding an agent adapted to effect deposit of the deterrent andthereafter evaporating the vehicle.

9. In the art of making propellant powders, the process comprising,treating powder grains with a deterrent dissolved in a volatile vehicle,adding an agent adapted to effect precipitation of the deterrent andsubsequently evaporating the vehicle.

10. In the art of making propellant powders, the process comprising,treating'powder grains with a deterrent carried in a volatile vehiclewhich is a solvent forthe powder grains and for the vehicle, adding anagent which is a non-solvent for the powder grains and for the deterrentand subsequently evaporating the vehicle.

11. In the art of making propellant powders, the process comprising,treating powder grains with a deterrent carried in a volatile vehicle,effecting deposit of the deterrent and subsequent- 1y heating the massat a temperature and for a period suflicient to evaporate the vehicleand to secure the desired ballistics.

12. In the art of making propellant powders, the process comprising,mixing a deterrent in a vehicle treating powder grains with onlysufficient of the mixture to wet the powder grains, and effectingdeposit ofthe deterrent on the grains in the presence of the vehicle.

13. In the art of making propellant powders, the process comprising,suspending a deterrent in a volatile vehicle treating powder grains withonly sufiicient of the deterrent suspension to wet the powder grains,efiecting deposit of the deterrent and thereafter evaporating thevehicle.

14. In the art of making propellant powders, the process comprising,immersing powder grains in a non-solvent bath, and slowly addingto thebath a deterrent carried in a vehicle, the nonsolvent and vehicle beingso selected as to effect precipitation of the deterrent upon contact.

15. In the art of making propellant powders, the process comprising,immersing powder grains in a non-solvent bath, and slowly adding to thebath a deterrent solution the solvent of which is completely misciblewith the non-solvent so as to precipitate the solute upon contact of thesolution with the bath.

16. In the art of making propellant powders,

the process comprising, immersing powder grains in a non-solvent bathand slowly adding to the bath a modifier solution the solvent of whichis so selected as to effect precipitation of the modifier upon contactwith the bath.

17. In the art of making propellant powders, the process comprising,agitating powder grains in an excess of non-solvent, and slowly droppinga solution of a modifier into the mixture.

18. In the art of making propellant powders, the process comprising,agitating powder grains in an excess of non-solvent, slowly dropping asolution of a modifier into the mixture to precipitate the modifier fromthe solution and thereafter evaporating the solvent.

19. In the art of making propellant powders,

the process comprising, agitating powder grains in an excess ofnon-solvent, and precipitating a modifier from a carrying vehicle in thenonsolvent and in the presence of the vehicle.

20. In the art of making propellant powders, the process comprising,agitating powder grains in an excess of non-solvent, and continuouslyprecipitating a modifier from a carrying vehicle in the non-solventduring agitation of the mixture, and thereafter removing the vehiclefrom the non-solvent.

GORDON C. TIBBITTS. FREDERICK R. SEAVEY.

